This invention relates generally to air filters for use with power tools, and particularly for use with tools, such as chain saws, which are powered by an internal combustion engine. More specifically, the invention relates to a unique housing assembly for enclosing an air filter to protect it from dust and debris while at the same time providing for uniform air flow around and through the filter.
As will be readily understood by those skilled in the art, it is imperative for good gasoline engine performance that clean, filtered air be supplied to the carburetor. It is, of course, known to provide filter elements for this purpose. However, in the environment of power tools, and especially chain saws, there are special problems related to the direct exposure of the air filter elements to significant amounts of dirt and debris generated by the tool itself during normal operation. For example, in the case of chain saws, filters often become clogged by dust, wood particles and even larger wood chips created by the cutting action of the saw. The problem is compounded by the presence of oil and grease around the engine, saw blade, etc. to which dirt and dust adhere.
Exposed filters, whether they be of the conventional foam or corrugated paper type, tend to draw air through paths of least resistance, so that the flow of air through the filter is not evenly distributed. As a result, the paths of least resistance are also the first to clog with dirt. This, if course, shortens the useful life (or periods between cleaning) of the filter, and negatively impacts on the performance of the engine. Moisture transfer through such exposed filters is an additional problem which may also adversely affect performance, and may even result in equipment failure.
Exposed filter elements are also subject to physical damage resulting from rough treatment of the tool, and/or flying debris, etc.
It is therefore the objective of this invention to provide protection for the filter element and to improve its performance by establishing a more uniform air flow around and through the filter, thus extending the life and/or time periods between required cleanings.
To effect this objective, the present invention provides a housing assembly for enclosing an air cleaner element, and an associated flexible coupling element for mounting the assembly to the engine. The flexible coupling provides additional benefits insofar as it is designed to break, or pull away from the engine upon impact, thus minimizing or preventing damage to the filter element and housing assembly, or the engine, or both.
The housing assembly of this invention comprises, in one exemplary embodiment, upper and lower annular components releasably secured together, with an annular filter element sandwiched therebetween.
The lower component comprises a centrally arranged, upstanding and slightly inwardly tapered hollow or tubular hub portion, and a peripheral flange extending radially outwardly from the lowermost end of the hub portion. The peripheral flange is provided with a plurality of apertures adjacent the outermost edge of the flange, and extending about the entire annular periphery thereof.
The uppermost end of the hub portion is provided with a relatively small, radially inwardly directed flange which supports a pair of diametrically opposed, upstanding threaded stud fasteners.
The upper housing assembly component in this exemplary embodiment has the general configuration of a slightly tapered inverted cup. Thus, an uppermost, substantially horizontal top wall surface is provided, having a downwardly extending and outwardly tapering peripheral skirt portion which terminates in a downwardly extending peripheral lip, radially offset from the depending skirt portion by a short, radially outwardly extending flange or step.
The substantially horizontal top wall surface may be provided with a centrally located indented portion provided with a pair of diametrically opposed apertures.
The filter element per se forms no part of this invention, other than in the context of its combination with the housing assembly described above. In any event, the filter element with which the housing of this invention is designed to be used has a open-ended cylindrical or tubular shape, wherein the outer diameter of the element exceeds its length. Typically, an annular, corrugated paper filter is sandwiched between a pair of rigid reinforcing rings formed of hard rubber, plastic, or the like.
Other filter elements may be used with the disclosed housing assembly, e.g., annular tapered filter elements may be received within the housing as well.
To assemble the housing components and associated filter element, the latter may be supported on the radially outwardly directed flange at the base of the hub portion of the lower component, with the hub portion extending upwardly into the interior of the filter element from below. The radially outwardly extending peripheral flange is sized so that the peripherally arranged apertures lie radially outwardly of the filter element.
The upper component of the housing assembly may then be placed over the filter element, such that the upper reinforcing ring of the filter is engaged by a radially outward portion of the substantially horizontal top wall, and so that the centrally located indented portion, if provided, extends slightly into the interior of the filter from above. At the same time, the outermost edge of the radially outwardly directed peripheral flange on the lower component abuts the flange or step portion connecting the depending skirt and lip portions of the upper component, with the lip extending downwardly, slightly beyond the radial edge of the peripheral flange of the lower component. The upwardly extending threaded stud fasteners, mounted in the hub portion of the lower component, are adapted to extend through the apertures in the indented area of the upper portion. The housing portions are then releasably secured together by the application of nuts of any suitable type to the threaded studs. It will be appreciated that the upper and lower housing components may be held together by any of a variety of suitable releasable connecting means.
It will also be appreciated that the upwardly extending wall of the hub portion of the lower component, and the depending skirt portion of the upper component, extend substantially parallel to one another, but in radially spaced relationship to accommodate the radial thickness of the air cleaner element.
Additional radial space is provided between the periphery of the air cleaner element and the depending skirt portion so that, in use, air may be pulled into the housing through the apertures in the radially outwardly extending flange of the lower component, uniformly about the entire periphery of the filter. Because the upper reinforcing ring of the filter element engages the top wall of the upper component, the incoming air is constrained to flow through the filter element and thereafter through the hub portion and associated coupling element to the carburetor as hereinafter described.
To facilitate mounting of the air cleaner and housing assembly to the engine of a power tool such as a chain saw, one or more couplers may be provided, depending on the configuration of the engine carburetor.
One coupler configuration in accordance with the invention is formed of a flexible tubular material, open at both ends, such that one end may be releasably attached to the filter housing assembly, and the other end may be releasably attached to the engine carburetor. In this configuration, the upper open end of the coupler is profiled about its exterior surface to provide a means cooperable with the inwardly directed radial flange provided at the upper end of the lower component hub portion to releasably secure the coupling to the filter housing. At the same time, the lower end of the coupler may be fitted with a metal ring-like adapter which may be clamped within the coupling and thereafter secured by screws or other suitable means to the carburetor. The particular sequence of assembly and attachment of the various components may vary as explained further herein.
In another coupling arrangement, a specific carburetor adapter may be molded in place within the lower portion of the coupler for ready attachment to the carburetor.
Because of the wide range of engine sizes and manufacturers in the chain saw field, the size and shape of the coupling elements may also vary. It is therefore within the scope of this invention to provide a coupling element which will adapt the filter housing assembly to any number of known engine and carburetor designs.
It will therefore be apparent that the invention provides a unique air filter housing assembly which protects the filter element, and enhances the performance of both the filter and the engine. Because of the great flexibility in the design of the coupling elements, the invention is easily adapted to fit virtually all chain saws, as original equipment or as a retrofit.